Installation guide

Cisco HWIC-4ESW and HWIC-D-9ESW EtherSwitch Interface Cards
How to Configure EtherSwitch HWICs
51
Cisco IOS Release 12.3(8)T4
OL-6454-01
Preventing the Forwarding of Dynamically Learned Stations
By default, the switch forwards any frames for stations that it has dynamically learned. By disabling this
activity, the switch only forwards frames whose addresses have been statically configured into the
forwarding cache.
Beginning in privileged EXEC mode, follow these steps to prevent the switch from forwarding frames
for stations that it has dynamically learned.
SUMMARY STEPS
1. configure terminal
2. no bridge bridge-group acquire
3. end
4. show running-config
5. copy running-config startup-config
DETAILED STEPS
To cause the switch to forward frames to stations that it has dynamically learned, use the bridge
bridge-group acquire global configuration command.
Configuring the Bridge Table Aging Time
A switch forwards, floods, or drops packets based on the bridge table. The bridge table maintains both
static and dynamic entries. Static entries are entered by you. Dynamic entries are entered by the bridge
learning process. A dynamic entry is automatically removed after a specified length of time, known as
aging time, from the time the entry was created or last updated.
If you are likely to move hosts on a switched network, decrease the aging-time to enable the switch to
quickly adapt to the change. If hosts on a switched network do not continuously send packets, increase
the aging time to keep the dynamic entries for a longer time and thus reduce the possibility of flooding
when the hosts send again.
Command Purpose
Step 1
configure terminal
Enters global configuration mode.
Step 2
no bridge bridge-group acquire
Enables the switch to stop forwarding any frames for stations that it has
dynamically learned through the discovery process and to limit frame
forwarding to statically configured stations.
The switch filters all frames except those whose destined-to addresses
have been statically configured into the forwarding cache. To configure
a static address, use the bridge bridge-group address mac-address
{forward | discard} global configuration command.
For bridge-group, specify the bridge group number. The range is 1
to 255.
Step 3
end
Returns to privileged EXEC mode.
Step 4
show running-config
Verifies your entry.
Step 5
copy running-config startup-config
(Optional) Saves your entry in the configuration file.